[PATCH] drm/ttm: fix missing NULL check in ttm_device_swapout

[Christian König]

Am 04.06.22 um 00:44 schrieb Felix Kuehling:
> [+amd-gfx]
>
>
> On 2022-06-03 15:37, Felix Kuehling wrote:
>>
>> On 2022-06-03 06:46, Christian König wrote:
>>> Resources about to be destructed are not tied to BOs any more.
>> I've been seeing a backtrace in that area with a patch series I'm 
>> working on, but didn't have enough time to track it down yet. I'll 
>> try if this patch fixes it.
>
> The patch doesn't apply on amd-staging-drm-next. I made the following 
> change instead, which fixes my problem (and I do see the pr_err being 
> triggered):
>
> --- a/drivers/gpu/drm/ttm/ttm_device.c
> +++ b/drivers/gpu/drm/ttm/ttm_device.c
> @@ -157,6 +157,10 @@ int ttm_device_swapout(struct ttm_device *bdev, 
> struct ttm_operation_ctx *ctx,
>                         list_for_each_entry(bo, &man->lru[j], lru) {
>                                 uint32_t num_pages = 
> PFN_UP(bo->base.size);
>
> +                               if (!bo->resource) {
> +                                       pr_err("### bo->resource is 
> NULL\n");
> +                                       continue;
> +                               }

Yeah, that should be functional identical.

Can I get an rb for that? Going to provide backports to older kernels as 
well then.

Regards,
Christian.

> ret = ttm_bo_swapout(bo, ctx, gfp_flags);
>                                 /* ttm_bo_swapout has dropped the 
> lru_lock */
>                                 if (!ret)
>
>>
>> Regards,
>>   Felix
>>
>>
>>>
>>> Signed-off-by: Christian König <christian.koenig at amd.com>
>>> ---
>>>   drivers/gpu/drm/ttm/ttm_device.c | 6 +++++-
>>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/ttm/ttm_device.c 
>>> b/drivers/gpu/drm/ttm/ttm_device.c
>>> index a0562ab386f5..e7147e304637 100644
>>> --- a/drivers/gpu/drm/ttm/ttm_device.c
>>> +++ b/drivers/gpu/drm/ttm/ttm_device.c
>>> @@ -156,8 +156,12 @@ int ttm_device_swapout(struct ttm_device *bdev, 
>>> struct ttm_operation_ctx *ctx,
>>>             ttm_resource_manager_for_each_res(man, &cursor, res) {
>>>               struct ttm_buffer_object *bo = res->bo;
>>> -            uint32_t num_pages = PFN_UP(bo->base.size);
>>> +            uint32_t num_pages;
>>>   +            if (!bo)
>>> +                continue;
>>> +
>>> +            num_pages = PFN_UP(bo->base.size);
>>>               ret = ttm_bo_swapout(bo, ctx, gfp_flags);
>>>               /* ttm_bo_swapout has dropped the lru_lock */
>>>               if (!ret)